Gumblar Botnet Resurfaces to Target Windows Users, ScanSafe Says

Compromised Websites are now being used to host malware exploiting Adobe software and Microsoft Windows security flaws. The move is the latest twist in the Gumblar attack campaign ScanSafe uncovered in May.

The Gumblar botnet is back with a new trick up its sleeve.
The goal, however, remains the same-to steal FTP credentials and other data.
Gumblar
first made the news in May, when attackers compromised legitimate sites and
sent visitors on to a malicious site that infected their PCs with malware. Now,
attackers
are using the legitimate sites they hack to host the malware itself instead
of relying on a malicious iFrame that points to the malware.

"In a typical outbreak situation, there are compromised Websites that
act as a conduit for malware hosted on an attacker-owned site," explained
Mary Landesman, senior security researcher at ScanSafe, on the company's Security Threat Alert Team blog Oct. 15. "But in this case,
the malware resides on thousands of legitimate (but compromised) Websites.

"There's no way of determining the total number of sites involved, but
judging by the number of blocks in our logs and the research we've done over
the past two days, I think it's safe to assume the number is in the low
thousands," Landesman continued.
The botnet was named Gumblar based on gumblar.cn, the malware domain
involved in the initial attacks. In addition to stealing FTP credentials, user names
and passwords, the malware is typically accompanied by another malicious
program that installs a backdoor on infected PCs. Meanwhile the stolen FTP
credentials are used by the attackers to compromise other Websites. The
attackers make configuration changes to the sites to lower security settings
and make them vulnerable to further attack even if the password is subsequently
changed, Landesman said.
Most of the compromised Websites are small and hosted in non-English-speaking
countries. Still, it is a pretty significant number since those pages are
actually playing host to the malware, she said.
"The attackers have uploaded the malware to match pre-existing
paths/filenames individual to each of the sites," she said. "For
example: sitename/images/image.gif will have an accompanying sitename/images/image.php
which contains the malware ... Thus the name and location of the malicious .php
file is unique to each individual compromised Website."
Landesman added that because the attackers are also using forums as a
conduit for the malware-and most likely manipulating search results as well-the
number of encounters with the malware is actually quite high, currently
accounting for 4.8 percent of all ScanSafe Web malware blocks.
So far, the exploits being used by the attackers revolve around Adobe Reader
and Adobe Flash Player, as well as the Microsoft Office Web Components
vulnerability described
in the MS09-043 security bulletin and the Microsoft DirectShow
vulnerability described in
MS09-011.
"As was the case in the original Gumblar attacks, the malware modifies
the following registry key: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows
NT\CurrentVersion\Drivers32," Landesman explained to eWEEK. "This
causes the malware to load when any sound-enabled application, i.e. any
browser, is launched. The malware also takes a read of sqlsodbc.chm, a file targeted by previous
Gumblar-delivered malware."